using Microsoft.Data.Sqlite;
using System;

namespace Elwig.Helpers {
    public static class AppDbUpdater {

        public static readonly int RequiredSchemaVersion = 3;

        private static int _versionOffset = 0;
        private static readonly Action<SqliteConnection>[] _updaters = new[] {
            UpdateDbSchema_1_To_2, UpdateDbSchema_2_To_3
        };

        private static void ExecuteNonQuery(SqliteConnection cnx, string sql) {
            using var cmd = cnx.CreateCommand();
            cmd.CommandText = sql;
            cmd.ExecuteNonQuery();
        }

        private static object? ExecuteScalar(SqliteConnection cnx, string sql) {
            using var cmd = cnx.CreateCommand();
            cmd.CommandText = sql;
            return cmd.ExecuteScalar();
        }

        public static string CheckDb() {
            using var cnx = AppDbContext.Connect();

            var applId = (long?)ExecuteScalar(cnx, "PRAGMA application_id") ?? 0;
            if (applId != 0x454C5747) throw new Exception("Invalid application_id of database");

            var schemaVers = (long?)ExecuteScalar(cnx, "PRAGMA schema_version") ?? 0;
            _versionOffset = (int)(schemaVers % 100);
            if (_versionOffset != 0) {
                // schema was modified manually/externally
                // TODO issue warning
            }
            UpdateDbSchema(cnx, (int)(schemaVers / 100), RequiredSchemaVersion);

            var userVers = (long?)ExecuteScalar(cnx, "PRAGMA user_version") ?? 0;
            var major = userVers >> 24;
            var minor = (userVers >> 16) & 0xFF;
            var patch = userVers & 0xFFFF;

            if (App.VersionMajor > major ||
                (App.VersionMajor == major && App.VersionMinor > minor) ||
                (App.VersionMajor == major && App.VersionMinor == minor && App.VersionPatch > patch))
            {
                long vers = (App.VersionMajor << 24) | (App.VersionMinor << 16) | App.VersionPatch;
                ExecuteNonQuery(cnx, $"PRAGMA user_version = {vers}");
            }

            return $"{major}.{minor}.{patch}";
        }

        private static void UpdateDbSchema(SqliteConnection cnx, int fromVersion, int toVersion) {
            if (fromVersion == toVersion) {
                return;
            } else if (fromVersion > toVersion) {
                throw new Exception("schema_version of database is too new");
            } else if (toVersion - 1 > _updaters.Length) {
                throw new Exception("Unable to update database schema: Updater not implemented");
            } else if (fromVersion <= 0) {
                throw new Exception("schema_version of database is invalid");
            }

            ExecuteNonQuery(cnx, "PRAGMA locking_mode = EXCLUSIVE");
            ExecuteNonQuery(cnx, "BEGIN EXCLUSIVE");
            for (int i = fromVersion; i < toVersion; i++) {
                _updaters[i - 1](cnx);
            }
            ExecuteNonQuery(cnx, "COMMIT");
            ExecuteNonQuery(cnx, "VACUUM");
            ExecuteNonQuery(cnx, $"PRAGMA schema_version = {toVersion * 100 + _versionOffset}");
        }

        private static void UpdateDbSchema_1_To_2(SqliteConnection cnx) {
            ExecuteNonQuery(cnx, "DROP VIEW v_area_commitment");
            ExecuteNonQuery(cnx, "ALTER TABLE delivery_part DROP COLUMN weighing_reason");
            ExecuteNonQuery(cnx, "ALTER TABLE delivery_part ADD COLUMN weighing_reason TEXT CHECK(NOT (manual_weighing = FALSE AND weighing_reason IS NOT NULL))");
        }

        private static void UpdateDbSchema_2_To_3(SqliteConnection cnx) {
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_1_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_2_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_3_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_4_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_5_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_6_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_7_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_8_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, "ALTER TABLE season ADD COLUMN bin_9_name TEXT DEFAULT NULL");
            ExecuteNonQuery(cnx, """
                UPDATE season
                SET bin_1_name = n.bucket_1_name,
                    bin_2_name = n.bucket_2_name,
                    bin_3_name = n.bucket_3_name,
                    bin_4_name = n.bucket_4_name,
                    bin_5_name = n.bucket_5_name,
                    bin_6_name = n.bucket_6_name,
                    bin_7_name = n.bucket_7_name,
                    bin_8_name = n.bucket_8_name,
                    bin_9_name = n.bucket_9_name
                FROM (SELECT year, bucket_1_name, bucket_2_name, bucket_3_name, bucket_4_name, bucket_5_name, bucket_6_name, bucket_7_name, bucket_8_name, bucket_9_name
                      FROM payment_variant GROUP BY year HAVING avnr = MAX(avnr)) AS n
                WHERE season.year = n.year
                """);
            ExecuteNonQuery(cnx, """
                CREATE TABLE delivery_part_bin (
                    year     INTEGER NOT NULL,
                    did      INTEGER NOT NULL,
                    dpnr     INTEGER NOT NULL,

                    bin_1 INTEGER DEFAULT NULL,
                    bin_2 INTEGER DEFAULT NULL,
                    bin_3 INTEGER DEFAULT NULL,
                    bin_4 INTEGER DEFAULT NULL,
                    bin_5 INTEGER DEFAULT NULL,
                    bin_6 INTEGER DEFAULT NULL,
                    bin_7 INTEGER DEFAULT NULL,
                    bin_8 INTEGER DEFAULT NULL,
                    bin_9 INTEGER DEFAULT NULL,

                    CONSTRAINT pk_delivery_part_bin PRIMARY KEY (year, did, dpnr),
                    CONSTRAINT fk_delivery_part_bin_delivery_part FOREIGN KEY (year, did, dpnr) REFERENCES delivery_part (year, did, dpnr)
                        ON UPDATE CASCADE
                        ON DELETE CASCADE
                ) STRICT;
                """);
            ExecuteNonQuery(cnx, """
                INSERT INTO delivery_part_bin
                      (year, did, dpnr, bin_1, bin_2, bin_3, bin_4, bin_5, bin_6, bin_7, bin_8, bin_9)
                SELECT year, did, dpnr, bucket_1, bucket_2, bucket_3, bucket_4, bucket_5, bucket_6, bucket_7, bucket_8, bucket_9
                FROM payment_delivery_part
                WHERE COALESCE(bucket_1, bucket_2, bucket_3, bucket_4, bucket_5, bucket_6, bucket_7, bucket_8, bucket_9) IS NOT NULL
                ON CONFLICT DO NOTHING;
                """);
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_1");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_2");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_3");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_4");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_5");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_6");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_7");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_8");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_delivery_part DROP COLUMN bucket_9");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_1_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_2_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_3_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_4_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_5_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_6_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_7_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_8_name");
            ExecuteNonQuery(cnx, "ALTER TABLE payment_variant DROP COLUMN bucket_9_name");

            ExecuteNonQuery(cnx, "DROP VIEW v_delivery");
            ExecuteNonQuery(cnx, """
                CREATE VIEW v_delivery AS
                SELECT s.*, GROUP_CONCAT(o.modid) AS modifiers
                FROM (SELECT p.year, p.did, p.dpnr,
                             d.date, d.time, d.zwstid, d.lnr, d.lsnr,
                             m.mgnr, m.family_name, m.given_name,
                             p.sortid, p.weight, p.kmw, ROUND(p.kmw * (4.54 + 0.022 * p.kmw), 0) AS oe, p.qualid, p.hkid, p.kgnr, p.rdnr,
                             p.qualid IN (SELECT l.qualid FROM wine_quality_level l WHERE NOT l.predicate AND (p.kmw >= l.min_kmw OR l.min_kmw IS NULL) ORDER BY l.min_kmw DESC LIMIT 1,100) AS abgewertet,
                             p.qualid NOT IN ('WEI', 'RSW', 'LDW') AS min_quw,
                             GROUP_CONCAT(a.attrid) AS attributes,
                             COALESCE(SUM(a.fill_lower_bins), 0) AS attribute_prio,
                             d.comment, p.comment AS part_comment
                    FROM delivery_part p
                        JOIN delivery d ON (d.year, d.did) = (p.year, p.did)
                        JOIN member m ON m.mgnr = d.mgnr
                        LEFT JOIN delivery_part_attribute pa ON (pa.year, pa.did, pa.dpnr) = (p.year, p.did, p.dpnr)
                        LEFT JOIN wine_attribute a ON a.attrid = pa.attrid
                    GROUP BY p.year, p.did, p.dpnr) s
                LEFT JOIN delivery_part_modifier o ON (o.year, o.did, o.dpnr) = (s.year, s.did, s.dpnr)
                GROUP BY s.year, s.did, s.dpnr
                ORDER BY s.year, s.did, s.dpnr;
                """);

            ExecuteNonQuery(cnx, "DROP VIEW v_bucket");
            ExecuteNonQuery(cnx, """
                CREATE VIEW v_delivery_bin AS
                SELECT year, mgnr,
                       sortid || IIF(min_quw, REPLACE(COALESCE(attributes, ''), ',', ''), '_') AS bin,
                       SUM(weight) AS weight
                FROM v_delivery
                GROUP BY year, mgnr, bin
                ORDER BY year, mgnr, LENGTH(bin) DESC, bin;
                """);

            ExecuteNonQuery(cnx, "ALTER TABLE wine_attribute ADD COLUMN fill_lower_bins INTEGER NOT NULL CHECK (fill_lower_bins IN (0, 1, 2)) DEFAULT 0");

            ExecuteNonQuery(cnx, "UPDATE delivery_part_bin SET bin_2 = bin_2 + bin_3, bin_3 = NULL WHERE bin_4 IS NULL");
        }
    }
}